Exercise volume and intensity: a dose–response relationship with health benefits

Introduction

The health benefits of exercise are well established. However, the relationship between exercise volume and intensity and health benefits remains unclear, particularly the benefits of low-volume and intensity exercise.

Purpose

The primary purpose of this investigation was, therefore, to examine the dose–response relationship between exercise volume and intensity with derived health benefits including volumes and intensity of activity well below international recommendations.

Methods

Generally healthy, active participants (n = 72; age = 44 ± 13 years) were assigned randomly to control (n = 10) or one of five 13-week exercise programs: (1) 10-min brisk walking 1×/week (n = 10), (2) 10-min brisk walking 3×/week (n = 10), (3) 30-min brisk walking 3×/week (n = 18), (4) 60-min brisk walking 3×/week (n = 10), and (5) 30-min running 3×/week (n = 14), in addition to their regular physical activity. Health measures evaluated pre- and post-training including blood pressure, body composition, fasting lipids and glucose, and maximal aerobic power (VO₂max).

Results

Health improvements were observed among programs at least 30 min in duration, including body composition and VO₂max: 30-min walking 28.8–34.5 mL kg^?1 min^?1, 60-min walking 25.1–28.9 mL kg^?1 min^?1, and 30-min running 32.4–36.4 mL kg^?1 min^?1. The greater intensity running program also demonstrated improvements in triglycerides.

Conclusion

In healthy active individuals, a physical activity program of at least 30 min in duration for three sessions/per week is associated with consistent improvements in health status.     

Acute hypoxic exercise does not alter post-exercise iron metabolism in moderately trained endurance athletes

Purpose

This study measured the influence of acute hypoxic exercise on Interleukin-6 (IL-6), hepcidin, and iron biomarkers in athletes.

Methods

In a repeated measures design, 13 moderately trained endurance athletes performed 5 × 4 min intervals at 90 % of their peak oxygen consumption velocity (vVO_2peak) in both normoxic [NORM, fraction of inspired oxygen (F _IO₂) = 0.2093, 15.3 ± 1.7 km h^?1] and simulated hypoxic (HYP, F _IO₂ = 0.1450, 13.2 ± 1.5 km h^?1) conditions. Venous blood samples were obtained pre-, post-, and 3 h post-exercise, and analysed for serum hepcidin, IL-6, ferritin, iron, soluble transferrin receptor (sTfR), and transferrin saturation.

Results

Peak heart rate was significantly lower in HYP compared with NORM (p = 0.01); however, the rating of perceived exertion was similar between trials (p = 0.24). Ferritin (p = 0.02), transferrin (p = 0.03), and IL-6 (p = 0.01) significantly increased immediately post-exercise in both conditions, but returned to baseline 3 h later. Hepcidin levels significantly increased in both conditions 3 h post-exercise (p = 0.05), with no significant differences between trials. A significant treatment effect was observed between trials for sTfR (p = 0.01), but not iron and transferrin saturation.

Conclusion

Acute exercise in hypoxia did not influence post-exercise IL-6 production, hepcidin activity or iron metabolism compared with exercise at the same relative intensity in normoxia. Hence, acute exercise performed at the same relative intensity in hypoxia poses no further risk to an athlete’s iron status, as compared with exercise in normoxia.     

The impact of high-intensity intermittent exercise on resting metabolic rate in healthy males

Introduction

High-intensity intermittent exercise training (HIT) may favourably alter body composition despite low training volumes and predicted energy expenditure (EE).

Purpose

To characterise the acute impact of two common HIT protocols on EE and post-exercise oxygen consumption (11 h EPOC).

Methods

Oxygen consumption (l min^?1), respiratory exchange ratio (RER) and EE were measured in nine healthy, lean males over 12 h under three conditions: control (CON), HIT1 (10 × 1 min high-intensity cycling bouts followed by 1 min rest) and HIT2 (10 × 4 min high-intensity cycling bouts followed by 2 min rest).

Results

Total exercise period EE during HIT1 (1,151 ± 205 kJ) (mean ± SD) was significantly lower than HIT2 (2,788 ± 322 kJ; p < 0.001). EE within the 60 min after exercise was significantly albeit marginally higher after HIT1 (388 ± 44 kJ; p = 0.02) and HIT2 (389 ± 39 kJ; p = 0.01) compared with CON (329 ± 39 kJ), with no difference between exercise conditions (p = 0.778). RER during this period was significantly lower in HIT1 (0.78 ± 0.06; p = 0.011) and HIT2 (0.76 ± 0.04; p = 0.004) compared with CON (0.87 ± 0.06). During the ‘slow phase’ of EPOC (1.25–9.75 h), there were no significant differences in EE (p = 0.07) or RER (p = 0.173) between trials.

Conclusions

Single HIT sessions notably increases EE during exertion; however, the influence on metabolic rate post-exercise is transient and relatively minor.     

Lateral lingual vascular canals of the mandible: a CBCT study of 500 cases

Purpose

The aim of the present study was to use cone-beam computed tomography (CBCT) images of patients to assess the localization, diameter, and course of the lateral lingual vascular canal (LLVC).

Methods

CBCT (Morita, Accuitomo 170) images from 500 patients were used in the present study. The CBCT images were examined by two oral radiologists. The diameter, localization, and course of the LLVCs were assessed using axial, cross-sectional, and multiplanar reformatted images. Statistical analysis was performed using SPSS^® v. 15 (SPSS Inc., Chicago, IL, USA), and t tests were used for statistical analysis.

Results

Of the 500 patients examined, 163 LLVCs were detected in 124 (24.8 %) cases. The mean diameter of LLVCs on the right side and left side was 0.65 ± 0.18 and 0.64 ± 0.17 mm, respectively. The majority of the LLVCs (n = 106, 83 %) were observed in the premolar region. There was a statistically significant difference between the occurrence of LLVCs in the premolar region and the other areas (p < 0.01).

Conclusions

All the LLVCs observed in this study had a connection with inferior alveolar canal structures. The detection of an LLVC on CBCT images should alert the radiologist and surgeons to the possible presence of collateral arterial and vascular structures.     

Operating lung volumes are affected by exercise mode but not trunk and hip angle during maximal exercise

Introduction

Despite VO_2peak being, generally, greater while running compared to cycling, ventilation (V _E) during maximal exercise is less while running compared to cycling. Differences in operating lung volumes (OLV) between maximal running and cycling could be one explanation for previously observed differences in V _E and this could be due to differences in body position e.g., trunk/hip angle during exercise.

Purpose

We asked whether OLV differed between maximal running and cycling and if this difference was due to trunk/hip angle during exercise.

Methods

Eighteen men performed three graded maximal exercise tests; one while running, one while cycling in the drop position (i.e., extreme hip flexion), and one while cycling upright (i.e., seated with thorax upright). Resting flow-volume characteristics were measured in each body position to be used during exercise. Tidal flow-volume loops were measured throughout the exercise.

Results

V _E during maximal running (148.8 ± 18.9 L min^?1) tended to be lower than during cycling in the drop position (158.5 ± 24.7 L min^?1; p = 0.07) and in the upright position (158.5 ± 23.7 L min^?1; p = 0.06). End-inspiratory and end-expiratory lung volumes (EILV, EELV) were significantly larger during drop cycling compared to running (87.1 ± 4.1 and 35.8 ± 6.2 vs. 83.9 ± 6.0 and 33.0 ± 5.7 % FVC), but only EILV was larger during upright cycling compared to running (88.2 ± 3.5 % FVC). OLV and V _E did not differ between cycling positions.

Conclusion

Since OLV are altered by exercise mode, but cycling position did not have a significant impact on OLV, we conclude that trunk/hip angle is likely not the primary factor determining OLV during maximal exercise.     

NLRP3 gene is associated with ulcerative colitis (UC), but not Crohn’s disease (CD), in Chinese Han population

Objective

This study aimed to investigate whether NLRP3 is associated with IBD in Chinese Han population.

Methods

Three SNPs were genotyped using polymerase chain reaction with sequence-specific primers in 288 patients [232 Crohn’s disease (CD) patients, 56 ulcerative colitis (UC) patients] and 274 controls.

Results

In IBD group, the results showed no significant association. When subdivided to CD and UC, it showed in CD subgroup, there was no significant association. However, in UC subgroup, rs10754558 (P _allele = 0.015272, P _genotype = 0.029776, OR [95 % CI] = 0.604190[0.401200–0.909886]) and rs10925019 (P _allele = 0.013042, P _genotype = 0.037045, OR [95 % CI] = 2.022613[1.149854–3.557812]) have significant associations with UC. The G and T alleles were risk factors of the susceptibility of UC, the GG and TT genotypes may increase risk of this disease. Rs4925648 has no association with UC. The haplotypes analysis results showed as follow: for rs4925648–rs10925019, CC and TT are risk factors for UC (for CC, χ ² = 3.605, P = 0.057613, OR [95 % CI] = 1.645 [0.980–2.761], for TT, χ ² = 5.522, P = 0.018804, OR [95 % CI] = 0.426[0.205–0.884]), and for rs10754558–rs10925019, CT and GC haplotypes are risk factors for UC (for CT, χ ² = 3.545, P = 0.059739, OR [95 % CI] = 0.571[0.317–1.029], for GC, χ ² = 9.359, P = 0.002228, OR [95 % CI] = 1.904 [1.255–2.887]).

Conclusions

We first demonstrated that rs10754558 and rs10925019 are significantly associated with the susceptibility of UC, but not CD in Chinese Han population, suggesting that NLRP3 may play an important role in the pathogenesis of UC.     

Small-sided games training reduces CRP,IL-6 and leptin in sedentary,middle-aged men

Purpose

Long-term physical activity is reported to improve chronic systemic inflammation, which provides protection against the ensuing development of chronic disease. Accordingly, the present study assessed changes in pro- and anti-inflammatory cytokines, aerobic capacity and body composition following 8 weeks of either small-sided games (SSG) or cycling (CYC) training compared to a sedentary control (CON) condition.

Methods

Thirty-three middle-aged, sedentary men were randomized into CYC (n = 11), SSG (n = 11), or CON (n = 11) conditions. The CYC and SSG conditions trained 3 days/week for 8 weeks, whilst CON maintained habitual activity and dietary patterns. Pre- and post-intervention testing included a dual-energy X-ray absorptiometry scan, sub-maximal (80 % maximal heart rate) aerobic capacity (VO₂) and fasting venous blood. Venous blood measures for pro-inflammatory markers included C-reactive protein (CRP), interleukin (IL)-6, IL-1β, tumor necrosis factor-α, and leptin; anti-inflammatory markers included IL-10, IL-1 receptor agonist, and adiponectin.

Results

Both CYC and SSG increased submaximal power output and VO₂ (P < 0.05), decreased total body fat-mass (TB-FM; P < 0.05), and CRP (SSG, ?0.45 ± 0.42 mg L^?1; P = 0.008; CYC, ?0.44 ± 0.59 mg L^?1; P = 0.02). Only SSG increased total body fat-free mass (TB-FFM; +1.1 ± 1.2 kg; P = 0.001) and decreased concentration of plasma IL-6 (?0.69 ± 0.62 pg mL^?1; P = 0.002) and leptin (?2,212 ± 2,531 ng mL^?1; P = 0.014).

Conclusion

Cycling and SSG training were both effective at improving CRP, VO₂ and TB-FM. Furthermore, SSG training has also shown to be an effective training approach in reducing IL-6 and leptin and increasing muscle mass within sedentary, middle-aged men.     

Short-term high-intensity interval and continuous moderate-intensity training improve maximal aerobic power and diastolic filling during exercise

Purpose

This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on cardiac function in young, healthy men.

Methods

Sixteen previously untrained men (mean age of 25.1 ± 4.1 years) were randomly assigned to HIT and CMT (n = 8 each) and assessed before and after six sessions over a 12-day training period. HIT consisted of 8–12 intervals of cycling for 60 s at 95–100 % of pre-training maximal aerobic power ( $\dot{V}$ O_2max), interspersed by 75 s of cycling at 10 % $\dot{V}$ O_2max. CMT involved 90–120 min of cycling at 65 % pre-training $\dot{V}$ O_2max. Left ventricular (LV) function was determined at rest and during submaximal exercise (heart rate ~105 bpm) using two-dimensional and Doppler echocardiography.

Results

Training resulted in increased calculated plasma volume (PV) in both groups, accompanied by improved $\dot{V}$ O_2max in HIT (HIT: from 39.5 ± 7.1 to 43.9 ± 5.5 mL kg^?1 min^?1; CMT: from 39.9 ± 5.9 to 41.7 ± 5.3 mL kg^?1 min^?1; P < 0.001). Resting LV function was not altered. However, increased exercise stroke volume (P = 0.02) and cardiac output (P = 0.02) were observed, secondary to increases in end-diastolic volume (P < 0.001). Numerous Doppler and speckle tracking indices of diastolic function were similarly enhanced during exercise in both training groups and were related to changes in PV.

Conclusion

Short-term HIT and CMT elicit rapid improvements in $\dot{V}$ O_2max and LV filling without global changes in cardiac performance at rest.     

The validity of the Moxus Modular metabolic system during incremental exercise tests: impacts on detection of small changes in oxygen consumption

Purpose

We investigated the accuracy of the Moxus Modular Metabolic System (MOXUS) against the Douglas Bag Method (DBM) during high-intensity exercise, and whether the two methods agreed when detecting small changes in $\dot{V}{\text{O}}_{2}$ between two consecutive workloads ( $\Delta {\dot{{V}}\text{O}}_{ 2}$ ).

Methods

Twelve trained male runners performed two maximal incremental running tests while gas exchange was analyzed simultaneously by the two systems using a serial setup for four consecutive intervals of 30 s on each test. Comparisons between methods were performed for $\dot{V}{\text{O}}_{2}$ , ${\dot{{V}}}_{\text{E}}$ , fractions of expired O₂ (FeO₂) and CO₂ (FeCO₂) and $\Delta {\dot{{V}}\text{O}}_{ 2}$ .

Results

The MOXUS produced significant higher (mean ± SD, n = 54) readings for $\dot{V}{\text{O}}_{2}$ (80 ± 200 mL min^?1, p = 0.005) and ${\dot{{V}}}_{\text{E}}$ (2.9 ± 4.2 L min^?1, p < 0.0001), but not FeO₂ (?0.01 ± 0.09). Log-transformed 95 % limits of agreement for readings between methods were 94–110 % for $\dot{V}{\text{O}}_{2}$ , 97–108 % for $\dot{V}_{\text{E}}$ and 99–101 % for FeO₂. $\Delta \dot{V}{\text{O}}_{2}$ for two consecutive measurements was not different between systems (120 ± 110 vs. 90 ± 190 mL min^?1 for MOXUS and DBM, respectively, p = 0.26), but agreement between methods was very low (r = 0.25, p = 0.12).

Discussion

Although it was tested during high-intensity exercise and short sampling intervals, the MOXUS performed within the acceptable range of accuracy reported for automated analyzers. Most of the differences between equipments were due to differences in $\dot{V}_{\text{E}}$ . Detecting small changes in $\dot{V}{\text{O}}_{2}$ during an incremental test with small changes in workload, however, might be beyond the equipment’s accuracy.     

Low-volume,high-intensity,aerobic interval exercise for sedentary adults: \dot{V}O2max,cardiac mass,and heart rate recovery

Purpose

The aim of this study was to compare the effects of low-volume, high-intensity aerobic interval training (HAIT) on maximal oxygen consumption ( \(\dot{V}\) O_2max), left ventricular (LV) mass, and heart rate recovery (HRR) with high-volume, moderate-intensity continuous aerobic training (CAT) in sedentary adults.

Methods

Twenty-four healthy but sedentary male adults (aged 29.2 ± 7.2 years) participated in an 8-week, 3-day a week, supervised exercise intervention. They were randomly assigned to either HAIT (18 min, 180 kcal per exercise session) or CAT (45 min, 360 kcal). \(\dot{V}\) O_2max, LV mass (3T-MRI), and HRR at 1 min (HRR-1) and 2 min (HRR-2) after maximal exercise were measured pre- and post-intervention.

Results

Changes in \(\dot{V}\) O_2max during the 8-week intervention were significant (P < 0.01) in both groups (HAIT, 8.7 ± 3.2 ml kg^?1 min^?1, 22.4 ± 8.9 %; CAT, 5.5 ± 2.8 ml kg^?1 min^?1, 14.7 ± 9.5 %), while the \(\dot{V}\) O_2max improvement in HAIT was greater (P = 0.02) than in CAT. LV mass in HAIT increased (5.1 ± 8.4 g, 5.7 ± 9.1 %, P = 0.05), but not in CAT (0.9 ± 7.8 g, 1.1 ± 8.4 %, P = 0.71). While changes in HRR-1 were not significant in either group, change in HRR-2 for HAIT (9.5 ± 6.4 bpm, 19.0 ± 16.0 %, P < 0.01) was greater (P = 0.03) than for CAT (1.6 ± 10.9 bpm, 3.9 ± 16.2 %, P = 0.42).

Conclusions

This study suggests that HAIT has potential as a time-efficient training mode to improve cardiorespiratory capacity and autonomic nervous system function in sedentary adults.     

Atrial functional and geometrical remodeling in highly trained male athletes: for better or worse?

Purpose

Highly trained athletes have an increased risk of atrial arrhythmias. Atrial geometrical and functional remodeling may be the underlying substrate. We analyze and relate atrial size, deformation and performance in professional handball players compared with non-sportive subjects.

Methods

24 Professional handball players and 20 non-sportive males were compared. All subjects underwent an echocardiographic study with evaluation of left (LA), right atrial (RA) dimensions and deformation by strain (Sa) and strain rate (SRa). Atrial performance was assessed from the atrial stroke volume (SV). With computational geometrical models, we studied the relation between atrial volumes, strains and SV and compared atrial working conditions. We estimated the functional reserve and a resulting average wall stress.

Results

LA and RA volumes were larger in athletes than in controls (35.2 ± 8.8 vs. 24.8 ± 4.3 ml/m², p < 0.01 and 29.0 ± 8.4 vs. 19.0 ± 5.1 ml/m², p < 0.01 respectively). LASa and RASa during active atrial contraction were decreased in athletes (?12.2 ± 2.0 vs. ?14.5 ± 2.1 %, p < 0.01 and ?12.1 ± 1.8 vs. ?14.2 ± 1.5 %, p < 0.01 respectively). LASV was similar between groups (6.6 ± 1.4 vs. 7.3 ± 1.1 ml, p = 0.19) and RASV was lower in athletes (6.2 ± 1.3 vs. 7.2 ± 1.1 ml, p < 0.01). Computational models showed that this different operational mode potentially increases performance reserve, but at the cost of higher atrial wall stress.

Conclusion

A proportion of athletes with enlarged LA and RA showed different atrial contractile performance, likely resulting in atria working at higher wall stress.     

TLR4 inhibition impairs bacterial clearance in a therapeutic setting in murine abdominal sepsis

Objective and design

To investigate the therapeutic effect of E5564 (a clinically used TLR4 inhibitor) in murine abdominal sepsis elicited by intraperitoneal infection with a highly virulent Escherichia coli in the context of concurrent antibiotic therapy.

Methods

Mice were infected with different doses (~2 × 10⁴–2 × 10⁶ CFU) of E. coli O18:K1 and treated after 8 h with ceftriaxone 20 mg/kg i.p. combined with either E5564 10 mg/kg i.v. or vehicle. For survival studies this treatment was repeated every 12 h. Bacterial loads and inflammatory parameters were determined after 20 h in peritoneal lavage fluid, blood, liver and lung tissue. Plasma creatinin, AST, ALT and LDH were determined to assess organ injury.

Results

E5564 impaired bacterial clearance under the antibiotic regime after infection with a low dose E. coli (1.7 × 10⁴ CFU) while renal function was slightly preserved. No differences were observed in bacterial load and organ damage after infection with a tenfold higher (1.7 × 10⁵ E. coli) bacterial dose. While treatment with E5564 slightly attenuated inflammatory markers provoked by the sublethal doses of 104–105 E. coli under the antibiotic regime, it did not affect lethality evoked by infection with 1.7 × 106 E. coli.

Conclusions

The impact of TLR4 inhibition during abdominal sepsis by virulent E. coli bacteria is only beneficial at low infection grade at cost of bactericidal activity.     

Influence of blood donation on the incidence of plateau at \dot{V}{\text{O}} 2max

Purpose

The purpose of this study was to examine the effects of reductions in blood volume and associated oxygen-carrying capacity on the incidence of plateau at $\dot{V}{\text{O}}$ _2max.

Methods

Fifteen well-trained athletes (age 23.3 ± 4.5; mass 77.4 ± 13.1 kg, height 180.1 ± 6.0 cm) completed three incremental cycle tests to volitional exhaustion, of which the first was defined as familiarisation, with the remaining two trials forming the experimental conditions of pre- (UBL) and post-(BLE) blood donation (~450 cm³). The work rate for the incremental tests commenced at 100 W for 60 s followed by a ramp of 0.42 W s^?1, with cadence being held constant at 80 rpm. Throughout all trials, $\dot{V}{\text{O}}$ ₂ was determined on a breath-by-breath basis using a pre-calibrated metabolic cart. The criteria for plateau determination was a ? $\dot{V}{\text{O}}$ ₂ ≤ 50 ml min^?1 over the final two consecutive 30 s sampling periods.

Results

Despite a significant (P = 0.0028) 9.4 % reduction in haemoglobin concentration and 10.8 % (P = 0.016) reduction in erythrocyte count between UBL and BLE, there was no change in plateau incidence. However, significant differences were observed for both $\dot{V}{\text{O}}$ _2max (P = 0.0059) 51.3 ± 7.6 (UBL) 48.4 ± 7.9 ml kg^?1 min^?1 (BLE) and gas exchange threshold arrival time 383.4 ± 85.2 s (UBL) 349.2 ± 71.4 s (BLE) (P = 0.0028).

Conclusion

These data suggest that plateau at $\dot{V}{\text{O}}$ _2max is unaffected by O₂ availability lending support to the notion of the plateau being dependent on the anaerobic capacity and the classically orientated concept of $\dot{V}{\text{O}}$ _2max.     

Effects of high vs. moderate exercise intensity during interval training on lipids and adiponectin levels in obese young females

Purpose

We investigate the effects of 12-week interval training of moderate- or high-intensity exercise on blood lipids and plasma levels of adiponectin.

Methods

Thirty-four obese adolescent females [age = 15.9 ± 0.3 years; BMI and BMI-Z-score = 30.8 ± 1.6 kg/m² and 3 ± 0.3, respectively], were randomized to high-intensity interval training (HIIT, n = 11), moderate-intensity interval training (MIIT, n = 11), or a control group (CG, n = 12). Maximal oxygen uptake ( $\mathop V\limits^{.} {\text{O}}_{{2{\text{peak}}}}$ V . O 2 peak ), maximal aerobic speed (MAS), plasma lipids and adiponectin levels were measured in all subjects before and after training.

Results

Following the training program, in both training groups, body mass, BMI-Z-score, and percentage body fat (% BF) decreased, while $\mathop V\limits^{.} {\text{O}}_{{2{\text{peak}}}}$ V . O 2 peak and MAS increased. Low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and adiponectin levels were positively altered (?12.6 and ?7.4 %; 6.3 and 8.0 %; 35.8 and 16.2 %; high to moderate training program, respectively). Waist circumference, triglyceride and total cholesterol decreased only in HIIT group (?3.5; ?5.3 and ?7.0 %, respectively, in all P < 0.05). Significant decrease in the usual index of insulin resistance (HOMA-IR) occurred in HIIT and MIIT groups (?29.2 ± 5.3 and ?18.4 ± 8.6 %, respectively; P < 0.01).

Conclusion

The results show that HIIT positively changes blood lipids and adiponectin variables in obese adolescent girls, resulting in improved insulin sensitivity, as attested by a lower HOMA-IR, and achieving better results compared to moderate-intensity exercise.     

Acute hyperglycaemia does not alter nitric oxide-mediated microvascular function in the skin of adolescents with type 1 diabetes

Purpose

We assessed the impact of an acute bout of hyperglycaemia on nitric oxide (NO)-mediated microvascular function in the skin of adolescents with type 1 diabetes (T1DM).

Methods

Twelve subjects (12–18 years) with T1DM were randomised into a control (n = 6) or hyperglycaemia (n = 6) group. Hyperinsulinaemic clamps were used to manipulate blood glucose level (BGL). Following a baseline period, where all subjects were euglycaemic (20 min), the experimental phase began. During the experimental phase, BGL was elevated to 16.7 ± 0.9 mmol L^?1 in the hyperglyceamic group, while it was maintained at euglycaemia (5.5 ± 0.1 mmol L^?1) in the control group. Simultaneously, cutaneous microvascular function (% max cutaneous vascular conductance, CVC%) was assessed using laser Doppler fluxometry following stimulation of skin blood flow using localised heating (42 °C). To determine the NO contribution to skin blood flow, two microdialysis sites were assessed, one perfused with Ringers and the other with the NO blocker, NG-monomethyl-l-arginine (l-NMMA).

Results

In the hyperglycaemic group, acute increase in BGL was not associated with changes in skin blood flow (CVC% 82.4 ± 8.7 % at 5.5 ± 0.1 mmol L^?1 vs 79.5 ± 9.1 % at 16.7 ± 0.9 mmol L^?1, unpaired t tests, P = 0.588) or the contribution of NO to vasodilation.

Conclusions

These results suggest that, in our group of adolescents with type 1 diabetes, acute hyperglycaemia did not affect skin microvascular NO-mediated function.     

Cerebral hemodynamic characteristics of acute mountain sickness upon acute high-altitude exposure at 3,700 m in young Chinese men

Purpose

We aimed at identifying the cerebral hemodynamic characteristics of acute mountain sickness (AMS).

Methods

Transcranial Doppler (TCD) sonography examinations were performed between 18 and 24 h after arrival at 3,700 m via plane from 500 m (n = 454). A subgroup of 151 subjects received TCD examinations at both altitudes.

Results

The velocities of the middle cerebral artery, vertebral artery (VA) and basilar artery (BA) increased while the pulsatility indexes (PIs) and resistance indexes (RIs) decreased significantly (all p < 0.05). Velocities of BA were higher in AMS (AMS+) individuals when compared with non-AMS (AMS?) subjects (systolic velocity: 66 ± 12 vs. 69 ± 15 cm/s, diastolic velocity: 29 ± 7 vs. 31 ± 8 cm/s and mean velocity, 42 ± 9 vs. 44 ± 10 cm/s). AMS was characterized by higher diastolic velocity [V _{d_VA} (26 ± 4 vs. 25 ± 4, p = 0.013)] with lower PI and RI (both p = 0.004) in VA. Furthermore, the asymmetry index (AI) of VAs was significantly lower in the AMS + group [?5.7 % (21.0 %) vs. ?2.5 % (17.8 %), p = 0.016]. The AMS score was closely correlated with the hemodynamic parameters of BA and the V _{d_VA}, PI, RI and AI of VA.

Conclusion

AMS is associated with alterations in cerebral hemodynamics in the posterior circulation rather than the anterior one, and is characterized by higher blood velocity with lower resistance. In addition, the asymmetry of VAs may be involved in AMS.     

Adaptations of aortic and pulmonary artery flow parameters measured by phase-contrast magnetic resonance angiography during supine aerobic exercise

Purpose

Increased oxygen uptake and utilisation during exercise depend on adequate adaptations of systemic and pulmonary vasculature. Recent advances in magnetic resonance imaging techniques allow for direct quantification of aortic and pulmonary blood flow using phase-contrast magnetic resonance angiography (PCMRA). This pilot study tested quantification of aortic and pulmonary haemodynamic adaptations to moderate aerobic supine leg exercise using PCMRA.

Methods

Nine adult healthy volunteers underwent pulse gated free breathing PCMRA while performing heart rate targeted aerobic lower limb exercise. Flow was assessed in mid ascending and mid descending thoracic aorta (AO) and main pulmonary artery (MPA) during exercise at 180 % of individual resting heart rate. Flow sequence analysis was performed by experienced operators using commercial offline software (Argus, Siemens Medical Systems).

Results

Exercise related increase in HR (rest: 69 ± 10 b min^?1, exercise: 120 ± 13 b min^?1) resulted in cardiac output increase (from 6.5 ± 1.4 to 12.5 ± 1.8 L min^?1). At exercise, ascending aorta systolic peak velocity increased from 89 ± 14 to 122 ± 34 cm s^?1 (p = 0.016), descending thoracic aorta systolic peak velocity increased from 104 ± 14 to 144 ± 33 cm s^?1 (p = 0.004), MPA systolic peak velocity from 86 ± 18 to 140 ± 48 cm s^?1 (p = 0.007), ascending aorta systolic peak flow rate from 415 ± 83 to 550 ± 135 mL s^?1 (p = 0.002), descending thoracic aorta systolic peak flow rate from 264 ± 70 to 351 ± 82 mL s^?1 (p = 0.004) and MPA systolic peak flow rate from 410 ± 80 to 577 ± 180 mL s^?1 (p = 0.006).

Conclusion

Quantitative blood flow and velocity analysis during exercise using PCMRA is feasible and detected a steep exercise flow and velocity increase in the aorta and MPA. Exercise PCMRA can serve as a research and clinical tool to help quantify exercise blood flow adaptations in health and disease and investigate patho-physiological mechanisms in cardio-pulmonary disease.     

The influence of aerobic fitness on the recovery of peak power output

Purpose

The aims of this study were to evaluate the recovery kinetics of peak power output (PPO) following a maximal sprint, and to evaluate the influence of aerobic fitness on that recovery process.

Methods

On separate occasions, 16 well-trained men (age: 21 ± 3 years; height: 1.84 ± 0.05 m; and body mass: 78.8 ± 7.8 kg) performed a 30 s maximal sprint on a cycle ergometer, followed by a predetermined stationary rest period (5, 10, 20, 40, 80, and 160 s) and a subsequent 5 s sprint to determine PPO recovery kinetics. On another occasion, \({\dot V}{{\rm O}_{2}}\) was monitored during recovery from a 30 s sprint to provide a comparison with the recovery of PPO. Finally, subjects completed a \({\dot V}{{\rm O}_{2{\rm max}}}\) test to evaluate the influence of aerobic fitness on the recovery of PPO.

Results

Despite following similar time courses (F = 0.36, p = 0.558), and being well described by double-exponential models, the kinetic parameters of PPO and \({\dot V}{{\rm O}_{2}}\) in recovery were significantly different (p < 0.05). There was no significant relationship (r = 0.15; p = 0.578) between \({\dot V}{\rm O}_{2{\rm max}}\) and the time to achieve 50 % recovery of PPO. Moreover, there was no difference (p = 0.61) between the recovery kinetics of participants classified according to their \({\dot V}{\rm O}_{2{\rm max}}\) (59.4 ± 1.3 vs 48.5 ± 2.2 ml·kg^?1·min^?1).

Conclusion

Despite similar overall recovery kinetics, \({\dot V}{{\rm O}_{2}}\) and PPO show differences in key model parameters. Moreover, the recovery of PPO does not appear to be affected by aerobic fitness.     

Novel patterns for the growing main bronchi in the human fetus: an anatomical, digital and statistical study

Purpose

Intensive progress in prenatal medicine results in performing airway management in the fetus affected by life-threatening congenital malformations. This study aimed to examine age-specific reference intervals and growth dynamics for length, proximal and distal external transverse diameters, and projection surface areas of the two main bronchi at varying gestational ages, including their relative growth in length and projection surface area.

Materials and methods

Using anatomical dissection, digital image analysis and statistics, length, proximal and distal external transverse diameters, and projection surface areas of the right and left main bronchi were examined in 73 human fetuses (39 males, 34 females) aged 14–25 weeks, derived from spontaneous abortions and stillbirths.

Results

Statistical analysis showed no sex differences. Between the 14 and 25th week of gestation, the lengths of the right and left main bronchi increased from 1.43 ± 0.18 to 3.18 ± 0.39 mm, and from 2.97 ± 0.16 to 7.58 ± 1.95 mm, in accordance with the functions: $ y = - 4.850 + 2.452 x \; \text{ln}\left( {\text{Age}} \right) \pm 0.400\;{\text{and}}\;y = - 15.005 + 7.093x \; \text{ln} \left( {\text{Age}} \right) \pm 0.579 $ , respectively. The proximal external transverse diameters of the right and left main bronchi varied from 2.13 ± 0.41 to 4.24 ± 0.20 mm, and from 1.84 ± 0.06 to 3.67 ± 0.66 mm, following the logarithmic models: $ y = - 8.666 + 4.018x \; \text{ln}{\rm (Age)} \pm 0.367\;{\text{and}}\;y = - 6.938 + 3.305x{\text{ ln(Age) }} \pm 0.323 $ , respectively. The distal external transverse diameter rose from 2.09 ± 0.47 to 4.24 ± 0.20 mm, as $ y = - 8.723 + 4.021x{\text{ ln(Age)}} \pm 0.392 $ for the right main bronchus, and from 1.85 ± 0.04 to 3.67 ± 0.66 mm, like $ y = - 6.924 + 3.280x{\text{ ln(Age)}} \pm 0.348 $ for the left one. On either side, there were no statistically significant differences between values of the proximal and distal transverse diameters of the main bronchus. The projection surface areas of the right and left main bronchi ranged from 2.95 ± 0.19 to 13.34 ± 2.12 mm², and from 5.57 ± 0.21 to 28.52 ± 5.24 mm², as $ y = - 10.212 + 0.943x{\text{ Age}} \pm 1.739 $ and $ y = - 19.119 + 1.875x{\text{ Age}} \pm 3.054 $ . The two main bronchi revealed a proportionate increase in both length and projection surface area, since the right-to-left bronchial length ratio and the right-to-left bronchial projection surface area ratio were stable, 0.41 ± 0.07 and 0.47 ± 0.08, respectively, throughout the analyzed period.

Conclusions

The main bronchi show no sex differences. The right and left main bronchi grow logarithmically in length and external transverse diameter, and linearly in projection surface area. The right and left main bronchi evolve proportionately, with the right-to-left bronchial ratios of 0.41 ± 0.07 for length, and 0.47 ± 0.08 for projection surface area.     

Age difference in efficiency of locomotion and maximal power output in well-trained triathletes

Purpose

The aim of this study was to examine the influence of age on cycling efficiency and sprint power output in well-trained endurance masters athletes.

Methods

The investigation was conducted on 60 healthy well-trained triathletes separated into six separate groups (n = 10) depending on age: 20–29 years old; 30–39 years old; 40–49 years old; 50–59 years old; 60–69 years old; 70 years old. Each participant attended the laboratory on three separate occasions to perform (1) an incremental cycling test, (2) maximal peak sprint power test, involving three 5-s sprint efforts (3) and a 10-min sub-maximal cycling test for determination of cycling efficiency.

Results

Cycling efficiency decreased beyond 50 years (50–59 years compared with 20–29 years: ?7.3 ± 1.8 %; p < 0.05) and continued to decrease beyond 60 years (60–69 years compared with 50–59 years: ?10.7 ± 2.4 %; p < 0.05), no further decrease was observed after 70 years. A continuous impairment in maximal sprint power output was observed after the age of 50 years leading to an overall decrease of 36 % between 20–29 years and >70 years. Significant positive relationships were observed between maximal sprint power output and both cycling efficiency (r ² = 0.64, p < 0.05) and maximal aerobic power (r ² = 0.42 and p < 0.05).

Conclusion

The present data indicates a significant effect of ageing on cycling efficiency and maximal sprint power output after 50 years and a significant relationship was found between these two parameters.